The present invention relates to trackball units installed on operating panels of various kinds of equipment.
Various types of pointing devices are known in the prior art, such as trackballs and trackpads that are used for moving a cursor on a display screen. One advantage of these pointing devices is the significant ease of their operation. The pointing devices are therefore installed on operating panels of various kinds of equipment, such as computers, and used for moving the cursor on the display screen.
Since the equipment like a computer provided with a pointing device is usually used indoors, water seldom intrudes into a trackball unit incorporating a trackball. Therefore, electronic devices like photocouplers for detecting rotation of a ball do not fail due to water ingress into the equipment through the trackball unit, except in rare circumstances. For this reason, almost no consideration is given to water-resistant properties of the trackball unit in designing its structure.
Since commercially available trackball units are designed with little consideration to water resistance, it is normally impossible to employ them as a pointing device for moving a cursor on equipment to be installed on an open deck of a pleasure boat, for example.
Another problem of the trackball unit is that if any foreign matter, such as dust, enters the trackball unit, it is necessary to remove the foreign matter because it impedes smooth rotation of the ball. It is desirable that a user can easily remove the foreign matter in such cases. It is obvious that the capability of such user maintenance would enhance the convenience of the trackball.
In the light of the foregoing, it is an object of the invention to provide a trackball unit featuring good water resistance and user maintenance capabilities.
To achieve this object, a trackball unit of the invention for moving a cursor on a display screen comprises a spherical ball and a casing having a ball receptacle for accommodating the ball and a drain hole connecting the ball receptacle to the exterior of the casing.
As the casing has a drain hole connecting the ball receptacle to the exterior of the casing, water which has intruded into the trackball unit can be drained to its exterior through the drain hole. In this construction, even if water leaks into the trackball unit, it would not further intrude into equipment on which the trackball unit is installed through a gap made at a shaft mounting point of the trackball unit, for instance. Accordingly, photoelectric detectors and various other electronic components provided in the trackball unit and in the equipment are hardly exposed to water dripping or seepage or other form of water leakage. This provides enhanced water resistance and serves to prevent failures of the internal electronic components of the trackball unit and the equipment potentially caused by exposure to water.
In one aspect of the invention, the trackball unit further comprises a cover attached to the casing, wherein the cover has a generally circular hole in the center and is detachably fitted to the casing.
This construction allows user maintenance of the trackball unit, enabling a user to easily remove foreign matter, such as dust, which has entered the trackball unit.
In another aspect of the invention, the trackball unit further comprises a ring-shaped ball retainer placed between the cover and the ball, the ball retainer having elasticity.
The elastic ball retainer serves to hold the ball at a stable position inside the casing, so that it is possible to rotate the ball in a stable fashion even when the trackball unit is installed on a vertical surface, for example. Accordingly, the trackball unit of the invention ensures excellent operability one would normally expect from a trackball regardless of where the trackball unit is installed.
In still another aspect of the invention, the trackball unit further comprises a pipe connected to the drain hole.
This construction makes it possible to easily drain water which has intruded into the trackball unit to the exterior of the equipment on which the trackball unit is installed without adversely affecting internal components of the equipment.
These and other objects, features and advantages of the invention will become more apparent upon reading the following detailed description in conjunction with the accompanying drawings.